On large-area organic light-emitting diodes (OLEDs) a significant unequal distribution of temperature and luminance usually occurs. The unequal distribution results firstly in an unattractive luminous image. Secondly, brightness and temperature peaks bring about an intensified aging of individual regions of the luminous area of the OLED. A more uniform temperature distribution may improve the homogeneity of the luminous image and increase the lifetime of the OLED.
As a result of microcavity effects, OLEDs have a color shift in the emitted light over the viewing angle. Said color shift is undesirable from a product standpoint.
The OLEDs commercially available at the present time (for example the OLEDs having the designation ORBEOS from Osram) do not as yet contain any device for compensating for lateral temperature gradients. If appropriate, the design of a conventional OLED has recourse to so-called busbars, which primarily provide for a more uniform current distribution and, as a secondary effect, bring about a slight improvement in the lateral temperature distribution, although this is insufficient.
Furthermore, in an organic light-emitting diode a component architecture with heat dissipation via radiation is known, consisting of a thermal contact layer, a metal plate and a radiation layer (Cok et al., Journal of the SID 13/10, 2005, pages 849 et seq.).
In order to combat the aspect of color angle distortion in an OLED, approaches pursued hitherto include applying scattering films or scattering foils, optimizing the layer sequence of the OLED and increasing the optical transparency of the bottom contact.
Furthermore, in the case of an organic light-emitting diode, for the purpose of reducing the color angle distortion, it is known to provide a combination of a semitransparent top contact and a mirror applied at the rear side (also designated as remote cavity) (Proc Int Disp Workshops—Vol. 11, “White Multi-Photon Emission OLED without optical interference”, pages 1293 to 1296 (2004)).